Vacuum-tube circuits



Jan. 18, 1927. 1,614,482

K M. M ILVAIN VACUUM TUBE CIRCUITS Filed May 6, 1924 Evwemtoz KARL M, MAC lLVAlN 951 Ms/ a t omm Patented Jan." 18, I927.

UNITED STATES-PATENT OFFICE.

KARL M. MACILVAIN, OF NEW YORK, .1\ T. Y., ASSIGNOR T RADIO CORPORATION 01 i AMERICA, A CORPORATION OF DELAWARE.

' VACUUM-TUBE CIRCUITS.

Application filed May 6, 1924. Serial No. 711,377.

This invention relates to new and useful improvements in vacuum tube circuits, more particularly, to the supply circuits for heating the cathodes of vacuum tubes.

5 It is an object of this inventionto provide a new and improved arrangement whereby the necessity for adjustable rheostatsin vacuum'tube circuits is avoided It is afurther object of this inventionto provide means whereby any desired number of vacuum tubes may be lighted at the proper temperature without the adjustment of rheostats.

. 'It is another object of invention to 7 provide an arrangement adaptable to radioticular embodiments thereof and mode of operation, will best be understood by reference to the following description taken in connection with the accompanying drawing,

in which the single figure shows a circuit embodyin my invention.

-With tie so-called thoriated filament tubes now in general use,,it is important that the filament temperature be not allowed to exceed'a certain value. As these tubes are widely used as amplifiers in radio receiving apparatus, they are subject to operation 4 quite frequently by persons unskilled in their use and such persons frequently burn the tubes at muclrhigher than their rated voltage, which materially shortens the life of the tubes. The arrangement which I have shown makes it possible to utilize such tubes without danger of their being burned at excessive voltages by anyone, and where my invention is applied to radio receivers, it makes possible the simplification of the receiver by eliminating the necessity for rheostat knobs on the panel or elsewhere. Since the proper value of resistance to maintain normal filament voltage on the filaments is taken care of by m arrangement quite automatically and in ependently of any care 5 on the part of the operator, it is evident that my invention is of particular usefulness in radlo apparatus built for broadcast listeners. Referring more particularly to the draw- 1ng, T T andT designate the usual form of vacuum tubeshavingfilament F, grid G and plate P.

Since my invention relates particularly to the control of the filaments, the grid and plate circuits of the tubes have not been completed, but it will be evident that any suitable arrangement may be used. For instance, 'T may represent a detector tube, T the first audio "frequency amplifier and T a second audio frequency am lifier. r

If the tubes are so arrange it may be advisable under some conditions to use no audio, frequency amplification, connecting the telephones in the output of the tube T Under mother conditions, it may be advisable to connect the telephones in the output circuit of either tubes, T or T In order to avoid' unnecessary use 'of the tubes, I have provided automatic filament control jacks, J J, and J jack J being associated witli tube T J with T and J with T As shown, jacks J and J 2 are standard sevenspring jacks; whereas, J ,is a standard fourspr'ing jack. It will be understood that transformers or other suitable coupling means are interconnected with the jacks in the usual manner so that by inserting the telephone plug in jack J a all tubes are functionlng, being coupled in cascade by transformers or other suitable coupling. When the'telephone plug is inserted in jack J the transformer or other means coupling 7 tube T, to tube T is out out and the telephones are inserted ,inits place. A similar result is obtained by the insertion of the telephone plug in jack J,.

The filaments of all tubes are energized from battery B. Connected between .the

tube T In a similarmanner connection p 'traced' as follows: From the positive terfrom spring 2 of jack J 2 is made to the filament of tube T and a similar connection from spring 2 of jack J 3 to. the filament F of tube T 'The other filament terminals are connected together as shown and to the negative side of the battery. Spring 3 of jack J is connected to spring 2 of jack J 2 and spring 3 of jack J 5 is connected to spring 2 of jack J As shown, spring 20f each of'the jacks J and J, rests upon spring 3. It will now be seen that if the telephone plug is inserted injack J springs-1 and 2 of jack J will be forced into contact and a circuit may then be traced'from the positive terminal of battery B through the first section of resistance R to spring 1 of jack J 3 to spring 2 of the same to the filament F of tube T also, to spring 3 of jack J spring 2 of jack J to filament F of tube T and also to spring 3 of jack J spring 2 of jack J and filament F-of tube T i If the telephone plug be withdrawn from J and inserted in J thefcircuit formerly closed by springs 1 and 2 will now be open and the circuit may be traced as follows: From the positive terminal of battery B through two sections of resistance R to sprin 1 of jack J thence to spring 2 of jack 5,, to .filament F of tube T also, to spring 3 of jack J to spring 2 of jack J to filament F of tube T and thence to the battery.

If the telephone plug is withdrawn from jack J and inserted in J,, the circuit is opened. through jacks J and J 3 and maybe minal of battery B through the entire resistance R to spring 1 of jack J thence to sprin 2 of jack J thence through the filament F of tube T, and return. If the telephone plug is removed from jack J all circuits are opened.

The number of sections into which the resistance B should be divided and the value follows:

If the total number of tubes which it is desired to use is w and the resistance necessary to be inserted in series with all of the of each section may be easily ascertained" as tubes to insure proper voltage acrossthe.

filaments of each is Y, then for any number of tubes less than a: desired to be used and designated by n, the proper value of resistance R to be applied is equal to R multi:

plied. by For instance, if in the arsistance is equal to 2 1/3 3/2 or which is equal to 31/2. If only one tube is to be used, the proper value of resistance is-equal to 2 1/3X3/1 or 7.

It is obvious that the arrangement is applicable to any number oftubes and with the disclosure, which I have given, l one skilled in the art may easily work out such an arrangement.

Having described my invention, what I .all of the tubes necessary for operation of said indicating instrument when inserted in any of said jacks at the proper voltage for said tubes.

2. In radio signalling apparatus, the combination of a plurality of vacuum tubes, each having a filament adapted to be heated, a source of energy for heating all of said filaments, a resistance. in circuit with said source, a filament control jack associated with each of said tubes and A connections from intermediate points of said resistance to each of said jacks respectively, said intermediate points being so chosen that the voltage drop through said resistance is substantially constant regardless of the number of tubes in use.

3. In radio signalling apparatus, the combination of a plurality of vacuum tubes, each having a filament adapted to be heated, a source of energy for heating all of said filaments, a resistance in circuit with said source, a filament control jack associated with each of said tubes and comprising means for lighting all bf the tubes necessary for usewhen a telephone plug or the like is inserted in any one of said jacks, and connections from intermediate points of said resistance to each of said jacks respectively, said intermediate points being so chosen that the value of resistance included in circuit with said source is always given by the quantity rxwhere 1' 1s the reslstance necessary to be included in series with said source to supply the proper filament voltage to oneof said tubes alone, a: is the total number of said tubesand 'n is the number of tubes in use at any given time.

KARL M. MAOILVAIN. 

